texts:
Last night, I used my new Sony WX500 camera to get long exposure pictures of the sky from my backyard.  I used the "Heavens Above" app to find out when satellite flares would happen and I even got a great picture of the ISS passing overhead at roughly -2mag.  I was able to identify many flares that I had gotten pictures of when reviewing the pictures today.  However, this is where it gets odd.

Some moving "things" didn't match what was supposed to show according to the app.  Some were accidentally caught in the pictures I took, and I'm sure there aren't any flares that the app showed me.

What could they be?  Shooting stars?  Forgotten or broken satellites?


texts: Statistically, what would the average distance of the closest black hole be?

texts:
The closest confirmed black hole is several thousand light years away from earth. Our galaxy has about 100 billion stars. I didn't find any reliable information on the black hole count of ratio versus stars for our galaxy. Some sources say about one in a thousand.

I would like to estimate how close a black hole would be given the data we have. If I did the calculation myself, I would use the volume of the galaxy and the number of stars in it. This would give the average number of stars per some volume, and out of that, the average number of black holes per volume. The distribution of stars would also be have to taken into account, since our part of the galaxy isn't as densely populated. Out of this the statistically approximate distance of the closest black hole could be obtained.

Is anyone equipped with enough information to give me an estimate?

Basically what is needed is the ratio of black holes to stars for our galaxy and then list of x nearest stars and their distances, where x is the ratio.

(I'm asking this because black holes are object of interest, and will have to be visited in the future. Given that our space capabilities might be limited to a distance of a couple of dozens of light years in the near future, this number is interesting.)


texts:
I found two telescopes that i'd like to buy, but one has 900mm focal length ((Skywatcher Newton 114/900 EQ1)) and the other has 500mm focal length ((National Geographic Dobson N 114/500)).
My questions are:

What is the "recommended" focal length for observing deep sky?
Are there better telescopes in the same price range?


texts:
What is the period of unique horoscopes? In other words how long does it take before any configuration of the classical planets repeats?

The seven classical "wandering stars" are: Sun, Moon, Saturn, Jupiter, Mars, Venus, and Mercury.

Assume a horoscope is created by dividing the ecliptic into 12 equal regions and then for a particular day noting which region each of the 7 "wandering stars" is occupying relative to the earth. For example, a horoscope could be: Sun in Aries, Moon in Capricorn, Saturn in Taurus, Jupiter in Libra, Mars in Pisces, Venus in Aries, Mercury in Aries.

Since Saturn revolves around the sun once every 29 earth years, Jupiter every 12 years, and Mars 1.88 or so, multiplying together we have 654. So, relative to each, they would seem to repeat their configuration every 654 years.

This is potentially a complicated question which might require a simulation to determine the answer. For example, today (5 December 2016), the following is true for the tropical zodiac:

Sun in Sagittarius
Moon in Aquarius
Mercury in Capricorn
Venus in Capricorn
Mars in Aquarius
Jupiter in Libra
Saturn in Sagittarius

So, one instance of this problem would be to determine the next date at which this same configuration will next recur.


texts: What is the schedule for science runs of aLIGO (and VIRGO)?

texts:
Advanced LIGO seems to operate only intermittently. Is there a schedule for at what times it will be able to register new gravity waves? Even if no formal schedule is available, what main factors determine the scheduling?

I suppose VIRGO in Italy, to get started in 2016, will operate mostly simultaneously with aLIGO. Or would its design require another type of schedule?


texts:
I am reading "The Essential Cosmic Perspective" by Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit.
In Chapter 14, it is stated that an evidence of the presence of dark matter in our galaxy is that the rotational curve does not match that obtained from calculation.
In the calculation, the following formula is used
$$M_r=\frac{rv^2}{G}$$
where $M_r$ is the mass enclosed inside a radius $r$ from the galactic center.

My understanding is that the above equation is a result of the shell theorem. But we know that shell theorem applies to spherically symmetric mass distribution only, and most galaxies are disks. So why can we still do this?


texts: Can New Horizons be used to measure the distance to Betelgeuse (despite its fickle photocenter)?

texts:
The New Horizons spacecraft is almost 50 AU from Earth and near-simultaneous images taken by its telescope and one on Earth have demonstrated parallax without relying on the movement of Earth in it's orbit.
The simultaneity is important because measurements of Betelgeuse are confounded by its fickle photocenter†. It's apparent disk is lumpy and nonuniform; the "center of gravity" of intensity of its apparent disk moves around relative to its true center of mass. Simultaneous imaging from two widely separated positions using the same spectral bandpass could be used to try to address that problem.
Could this be done given what's known about its Long Range Reconnaissance Imager or LORRI and considering that the spacecraft has plenty of time on its hands?
Recent headlines saying that Betelgeuse is much closer than we thought point to Standing on the Shoulders of Giants: New Mass and Distance Estimates for Betelgeuse through Combined Evolutionary, Asteroseismic, and Hydrodynamic Simulations with MESA which proposes in the abstract

...a new, independent distance estimate of ${168}_{-15}^{+27}$ pc and a parallax of $\pi ={5.95}_{-0.85}^{+0.58}$ mas, in good agreement with Hipparcos but less so with recent radio measurements.

based on extensive modeling and photometric data.
What's truly remarkable is that I just copy/pasted that blurb and it self-formatted in MathJax, yay!
New Horizons is currently at X, Y, Z = 14.11, -46.42, 1.67 (AU) relative to the solar system barycenter in J2000.0 with ecliptic as reference plane using JPL's Horizons. I'm hoping that's orthogonal to Betelgeuse.

†fickle photocenter You can try to say that three times fast, but whatever you do, don't say the star's name three times!

Related:

What will it finally take to accurately measure the distance to Betelgeuse?
What equipment and techniques were used to study Betelgeuse's diameter in 1920?
How often are radio telescopes used to measure parallax? When was this first done? Currently unanswered.
Was a “spare LORRI” camera available to take matching image on Earth the same time New Horizons took the parallax image from the Kuiper belt? No conclusive answer yet, I really thought that there was one, and it might come in handy for this.


texts:
If the dark energy equation of state $\omega$ evolves with time, and becomes larger, this would result in decelerated expansion and eventually a Big Crunch. If $\omega$ decreases with time, becoming more negative, then a Big Rip would occur. I understand that the Big Rip has not yet been ruled out by current observations, but I often hear that the Big Crunch has been ruled out since we know the universe is expanding (and accelerating).

If the Big Rip can't currently be ruled out, then how can the Big Crunch be ruled out? Shouldn't they both still be on the table, unless we can somehow infer which direction $\omega$ evolves in under a quintessence model?


texts: Two body orbit dynamics for orbital periods approaching light cone limit

texts:
How do you model a system of two large celestial bodies, where they achieve a rotation very close to the limit at which information can escape the system (heat, light, etc.), do they begin to appear like toroids? Does the last parsec problem possibly discuss such things?

I am trying to take into consideration the object's radius as well.


texts: What is the distance of Earth from the 7 planets, moons and the Sun at a point of time?

texts:
I wanted to know the distance of the 7 planets (Mercury, Mars, Venus, Jupiter, Saturn, Uranus, Neptune ) each (or at least 5 planets) from the earth and the angle that it will make with a line connecting the centers of earth and the respective planet at a point of time. Also I need the same for the earth and moon system and sun and earth as they are big influences. At point of time because in the course of revolution of planets the distances with respect to earth will vary.

Being an engineering student I have the wish :) to calculate the mechanical forces acting on the earth at a point of time due to nearby heavenly bodies.

Basically I need the data or in case someone already attempted to calculate the force components I would be delighted to look at it.


texts: Dish antenna as parabolic mirror for OPTICAL telescope?

texts:
Can I use a chrome painted dish TV antenna as a parabolic reflector for my optical telescope? Given that glass mirrors are quite expensive, I am thinking of using a Dish TV antenna and coating its reflecting surface with chrome paint to give it a mirror finish. But I couldn't find any instance of it online. I did find several examples of people using a dish antenna for making an amateur radio telescope.

I was wondering if there is a reason why we can't use it in optical telescope.


texts: Could the KIC 8462852 (Alien megastructure star) be explained by orbiting gas clouds?

texts:
I was wondering about the light dimming of the 'alien megastructure' star.
From what I understand, for it to be a planetary body, it would have to be some 20 times the size of Jupiter.
Is it possible that it could be caused by some huge, dense gas cloud, orbiting around the star?


texts:
I found this picture and I am really wondering if it is possible for the moon to get as close to the earth as this picture shows?

( Super moon above Rio De Janeiro)


texts: Inability of Hubble to clearly resolve nearby celestial objects

texts:
The Hubble space telescope performs incredibly detailed and stunning imaging of celestial bodies that are many, many light years away, and yet when it attempts to image objects within our own Solar System, such as of Pluto and Charon, the results appear out of focus and smeared. Why is this so?

I can only guess that the objects within the Solar System have a higher relative intrinsic motion than objects light years away, and thus Hubble can't track them so precisely? Or maybe Hubble's optics are "fixed" at an "infinity point" beyond "nearby" objects? Or...?


texts: Why don't the stars in a binary star system of equal masses always orbit their center of mass in a circular orbit?

texts: If I have a binary object system of equal masses, why don't they always have the same circular orbit around their center of mass, like in the photo?


texts:
Is an ice planet made only by ice?
What causes the water to conglomerate and form ice in a planet?

Even if the planet is not made entirely by ice but has an high % of ice (e.g. 50% ice), how can it be explained?

I heard about ice planets with surface temperature way above the melting point.
Can it be explained with surface pressure?
Edit: This is probably wrong but feel free to point it out in a full answer

Thanks.


texts: What is this pale blue dot in a daytime photo of a Sun halo?

texts: This photo of the sun behind a cloud was taken on the south coast of England in early May 2021 using an iPhone 11. A halo is visible which I think is the 22-degree halo. However, the photo also shows a small, pale blue dot near the middle of the photo, within the photo, left and above the Sun. Please could somebody suggest what the blue dot is?


texts: In relation to Meteor Showers, what is meant by Lambda Omicron?

texts:
I see for example, the L.O. of the Quadrantids is 283.16 and Lyrids is 32.32.

src: https://en.wikipedia.org/wiki/List_of_meteor_showers


texts: How do people derive ionized gas mass from optical emission lines in a galaxy spectrum?

texts: Suppose you had an optical spectrum of a galaxy, and you unambiguously detected emission lines from cooling ionized gas -- both forbidden lines like [O II] 3727AA and [O III] 4959,5007AA, as well as recombination lines like H$\beta$. So you have measured things like the integrated flux, equivalent width ($\equiv$ integrated flux / local continuum flux density), FWHM, etc. for your emission lines. Now, you want to know how much warm ionized gas is in the galaxy (or at least in the region in which your spectrum was taken) -- i.e., you want to go from your aforementioned Gaussian parameters like integrated flux to a gas mass in solar masses. How do people typically do this, and what assumptions do you have to make? Any references would be greatly appreciated!


texts: Where did the "Is this object Mars" question go?

texts: That was an interesting question. Was it deleted? If so, why? The browser record links to Page not found. If it was moved to another SE, there should be a redirection or something.


texts:
If time slows down the closer you get to the speed of light, does it follow that time does not exist for photons. Do photons - even if they travel across billions of light years of space - arrive at the same time as they are created?
And if this is so, does this not explain the peculiarities of the double-slit experiment?


texts: Is the lower mass limit of a neutron star the same as the upper mass limit of a white dwarf?

texts: If not, when can a white dwarf be more massive than a neutron star?


texts: How to make motion of the Sun more apparent at seconds scale?

texts:
Each time I look at a shadow cast by a sunlit object it seems as if the shadow doesn't move at all. But if I look at it after say 5 minutes, I can notice that the shadow has actually moved a bit. This allows to say "yes, the Sun has moved in the sky". But this doesn't make it all that obvious that "the Sun is continuously moving all the time".

So I'd like to make some optical configuration which would allow me to watch a spot of sunlight or a shadow moving much faster — say, 1 mm/s — still being from the Sun, not from an artificial light source. I've tried doing this with a cylindrical silvery surface like that of a kitchen rail system, sticking black tape on it and leaving only a lateral strip of reflecting surface, then then letting Sun rays to hit it almost tangentially, and to observe the reflection. But either this doesn't give good enough magnification to make Sun's motion apparent, or the reflected spot just becomes too faint for the naked eye.

So, what can I do to effectively magnify angular motion of the Sun to observe it (almost) directly at the scale of seconds? I's OK if it could be visible for e.g. a minute and required me to adjust my instrument to view the next piece of motion. But I'd like to do it as simply as possible, without too expensive hardware.


texts: If we "turned universe upside-down" and changed all matter to anti-matter instantly

texts:
...what would be the immediate consequences?

Or putting it better, if (from big-bang or whathever), the universe were always made of what we call Anti-matter what would it be?

The scientists of this universe would call 'Matter' 'Anti-Matter'.

Will the universe looks like exactly the same? By "looks", I mean the laws of Physics, the constitution of the universe with its superclusters of galaxies containing clusters containing galaxies and so on...


texts: Derivation of a formula for the mass of a tidal bulge and tidal torque

texts:
I've been looking into the tidal mechanism for a binary star system and seem to have hit a brick wall. In the literature (see below), little explanation is given to justify the equations (9.60), (9.61) and (9.62). I would be grateful if someone could talk me through where these equations came from, as my efforts to find a complete and concise explanation online have thus far been fruitless. Note that I've had to cut some of the text at the top where the page turns over, but this is just a brief introduction to the use of Legendre polynomials in providing a tide raising part of the potential.

  Eldridge and Tout, The Structure and Evolution of Stars, 2019


texts:
There is somewhat of an abstract way of generalising the notion of planets.

Standard definition of planets is, obviously: "planets are the objects formed from the residual material surrounding a newly formed main sequence star through a complex formation process".

Let me introduce a bit more general, by no means commonly known, definition of "generalised planets as bound macroscopic objects formed from some former accretion process taking place near some gravitating body over many orbital periods".

Clearly, the latter definition is more general, as it doesn't specify the type of accretion event and the type of the central body. Now, for example, the accretion mechanism can be very different from that in protoplanetary discs: consider, for example, accretion on a compact object (a neutron star or a black hole), accrection on supermassive black hole, accretion from remnants of binary neutron stars merger, or any other possible accretion process.

As noted in some answers, some stars also form in accretion-involving processes in the vicinity of other stars. To avoid including stars into 'generalised planet' category, the definition specifies that the objects should be formed over many orbital periods, implying that they should be sufficiently bound with respect to the primary.

The question: Are there generalised planets other than planets/exoplanets?


texts: If GRB 080319B happened next to nearest star: Proxima Centauri, what effect would that have had on us?

texts:
From a Reddit post

GRB 080319B was a gamma-ray burst (GRB) detected by
the Swift satellite at 06:12 UTC on March 19, 2008. The burst set a
new record for the farthest object that was observable with the naked
eye: it had a peak visual apparent magnitude of 5.7 and remained
visible to human eyes for approximately 30 seconds. The magnitude was
brighter than 9.0 for approximately 60 seconds. If viewed from
1 AU away, it would have had a peak apparent magnitude of −67.57 (21
quadrillion times brighter than the Sun seen from Earth).
Wiki

Someone asked what would happen if that GRB happened from the distance of  Proxima Centauri, what effect would that have had on us?


texts: Is the rate of gravitational wave detection roughly what was expected?

texts:
LIGO's first light was back in 2002 but it has only recently started regular observation. With roughy 50 events confirmed, is it possible to compare its detection rate to predicted rates?
There were probably some wide ranges bracketed, and predictions may have evolved after construction began as the science evolved, so there can't be a precise answer. But is it possible to at least say if the rate is roughly in the same ballpark as what was anticipated?
Are there any glaring deficiencies or surprisingly high rates for specific types of events at all?

Observations are made in "runs". As of December 2019, LIGO has made 3 runs, and made 50 detections of gravitational waves. Maintenance and upgrades of the detectors are made between runs. The first run, O1, which ran from 12 September 2015 to 19 January 2016, made the first 3 detections, all black hole mergers. The second run, O2, which ran from 30 November 2016 to 25 August 2017, made 8 detections, 7 black hole mergers, and the first neutron star merger. The third run, O3 began on 1 April 2019; it is divided (so far) into O3a, from 1 April to 30 September 2019, and O3b, from 1 November 2019 until it was suspended in March 2020 due to COVID-19.


texts: Calculate depth and duration of exoplanet's transit using Python, astropy or lightkurve

texts:
I am creating a program for the analysis of exoplanets in Python using Astropy and Lightkurve libraries. I have light curve of specified star and I would like to calculate depth and duration of planet transit. There is example for Kepler 10 bellow with these steps:

Load target pixel image for Kepler 10,
Convert it to flattened time series,
Calculate period using periodogram,
Create folded light curve.

import lightkurve as lk

target_pixel = lk.search_targetpixelfile("Kepler-10", quarter=1).download()
lightcurve = target_pixel.to_lightcurve(aperture_mask=target_pixel.pipeline_mask).flatten()
periodogram = lightcurve.to_periodogram(method="bls", period=np.arange(0.5, 10, 0.001))
period = periodogram.period_at_max_power

folded.scatter()
print(period)

The output is (I marked the depth and duration in red):

Now, how can I calculate duration of transit (approximately from -0.15 to to 0 on x-axis)? Interval from -0.5 to 0.5 should be whole period (0.837 d), so transit duration should be +/- 0.13 d.

And what about transit depth? I was thinking about:

min = np.min(folded.flux)
median = np.median(folded.flux)
median / min - 1 # 0.00038

However, the minimum point is not the one in the middle of the transit due to noise, so transit depth may not be accurate.


texts: Are we moving ever closer to the center of our Galaxy due to a super massive black hole?

texts:
I've seen in documentaries that at the center of each galaxy is a super massive black hole which holds the galaxy together.

Since black holes have such a strong pull, are we slowly being pulled in closer and closer to this black hole?


texts: Can the shape and fluctuations of the heliopause be attributed to specific nearby stars and clusters?

texts:
The heliopause is where the Solar wind is counter balanced by the particle winds from other stars. This boundary seems to not be spherical and also to fluctuate in shape.

Can the shape of the heliopause be estimated by the pressure from surrounding stars and open clusters?

Can the fluctuations be attributed to specific stars in the Solar neighborhood? Are there single stars both so active and so nearby that they dominate the fluctuations of the Heliopause? Did Voyager in effect observe the effects of a specific event on a specific star's surface when the heliopause boundary billowed back and forth over it?


texts: Why 225088 Gonggong is not a dwarf Planet yet?

texts:
Per definition a dwarf planet is:

  a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape1, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

The Wikipedia page for 225088 Gonggong, former 2007 OR10 states three possibilities for its dimensions:

  1535+75−225 km
  1280+210−210 km
  1200+300−200 km

Which is all minimum 1000km in diameter. So how can you still doubt the hydrostatic equilibrium for such a large body?


texts: Will gravitational waves too far away ever reach us?

texts:
Gravity is the curvature of spacetime, and its effects travel at lightspeed. However, space is expanding; eventually, light from distant galaxies will become more and more redshifted, and we will no longer be able to see them (source).

As such, there is a limit to how far we could ever possibly see, since light too far will never reach us due to the rapid expansion of space...or at least, if I'm understanding this correctly.

Now, gravitational waves travel at lightspeed. So, after enough time, when an object's light no longer reaches us, will its gravity no longer affect us either?

A better rephrasing is: at a certain point in time, will the gravity of any extremely distant object — even the most massive stars, black holes, or galaxies — simply not affect us whatsoever, in the slightest?


texts: What is the closest candidate for Dark Matter currently?

texts:
I've both fascinated and frustrated after learning about the existence of Dark Matter.

Can we find evidence of Dark Matter within our Solar system? What is currently the closest candidate for Dark Matter?

And please let me know what are good online resources where I can stay up to date with information about this?


texts: Why did the moon abruptly change positions in the sky?

texts:
Three or four weeks ago I was outside showing my neighbors how cool the moon was through a 'backyard' telescope in broad daylight (~8PM PDT).  It was 3/4 of the way across the sky (setting behind the houses behind us.)  Two weeks later the moon was not even up yet at 8PM.  The planets I've been watching (Jupiter, Saturn, Mars) are all rising and setting a little earlier each day as I would expect.

Why did the moon abruptly change its position in the sky a couple of weeks ago?


texts: Why does titanium oxide around Betelgeuse produce this particular sawtooth-shaped absorption spectrum?

texts:
Betelgeuse Just Isn’t That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse suggests that the recent dimming might be caused by increased optical absorption by dust around the star, based on a spectral analysis.

Question: The images below show absorption features assigned to titanium oxide (TiO) around Betelgeuse. Why are these features saw-tooth shaped? When I think of absorption edges the transmitted light drops when crossing from lower to higher energy photons, but here the measured light increases from lower to higher energy.

note 1: A quick check shows that these shapes are typical, so it's really just a matter of me not understanding why these features have the particular shapes that they do.

note 2: There is some discussion of Betelgeuse's titanium lines in the second half of Scott Manley's Astronomers Think They Know Why Betelgeuse Got Dimmer

  Fig. 1.— Optical spectrophotometry of Betelgeuse from 2020 (black) and 2004 (red).

  Fig. 2.— Normalized and continuum-flattened spectra of Betelgeuse from 2020 (black) and 2004
  (red dashed), illustrating the relative depths of the Teff-sensitive TiO bands (labeled) in both spectra.


texts: Why is the Sun's brightness and radius increasing, but not its temperature?

texts:
On the Sun's article on Wikipedia, there is an image showing how the Sun's brightness, radius and temperature have changed over time:

For the past (and next) few billion years, I see the luminosity continuously rising, the temperature remaining about the same, and the radius also rising.

This seems bizarre to me. I would imagine that, for luminosity to increase, the temperature would have to increase. And for temperature to increase, the radius would have to decrease (as the core becomes denser, temperatures rise).

So why does it work this way?

PS: I would also appreciate a concrete explanation for why all three decreased at the beginning of the Sun's life, but suddenly began increasing.


texts: Could a "burping" supermassive black hole be responsible for a spiral galaxy's look?

texts:
I read an article which suggests black holes could influence the production of stars in the galaxy as the black hole can burst out powerful X-rays to "snowplow" the surrounding dust and gas.

Although the article didn't suggest that spiral galaxies are made this way, I like to think that a supermassive black hole that "burps" lies in the core of every spiral galaxies. Am I mistaken?

Complementary question: does the supermassive black holes inside the Milky Way still "burp" or it is already cured?


texts: Approximate spectral type and luminosity given apparent magnitude and distance

texts: I am looking at the data acquired from the Gaia DR2 survey. I found that most of the stars had their distance and apparent magnitude catalogued, but not their spectral type and luminosity class. Is there a way to approximate this?


texts: How much mass do the volcanoes of Io erupt past escape velocity?

texts:
While trying to do some calculations to answer this quesion, I got stuck missing a crucial piece of data: I have no clue how much mass the volcanoes of Io manage to throw out of the gravity well of the Jupiter moon.

It is clear that most of the erupted material falls back to the surface, and the various velocity estimates I have found are quite a bit lower than the escape velocity (~2.56 km/s). For instance "up to 1 km/s".

One number that is possible to find is how much mass the magnetosphere of Jupiter strips of Io. Most are listing that as 1000kg/s (example). That is about as much as the wheat production of Canada.

Are the volcanoes directly throwing away a lot more than that? A lot less? Not at all?


texts:
I'm researching high altitude photography and want to know a schedule for taking pictures of the moon.

Preferably I want a picture of the (full) moon on the horizon.

How would I go about scheduling such an event from a high altitude location?


texts: Meade ETX-90 with computerized mount slews too far during auto-alignment

texts:
I've been trying to get my new ETX-90 to properly align itself these past few nights, but without success.  I've mostly been using the Easy align functionality, which has been choosing Arcturus and Altair as target stars.  Arcturus can become obscured by trees later in the night from my viewing location, but I can see it early enough in the night to use it for aligning the telescope.

The problem, as the title suggests, is that when the telescope starts the alignment process, it slews right past Arcturus (and to a lesser extent, above it).  The same thing happens if I do manage to get a fix on Arcturus and continue on to Altair.  If I try, instead, to perform a two star alignment, choosing Altair as the first star, the telescope will slew over 180°.  In both cases, after fixing on both stars Autostar complains that I didn't perform the alignment correctly.

It seems like the gear ratios are incorrect, however I've verified that they are the factory defaults, and have even performed a reset.  I've also tried to calibrate the motors and train the drives, using a landmark about 100m from my viewing location, although I don't own an eyepiece with a reticle.  The time is correct, and the location should be close enough (within a few arc-minutes), so nothing else seems wrong with my setup.

This doesn't seem like a common problem, since none of my other research has turned up similar situations.  My most reasonable guess is that the gear ratios are in fact wrong, which would lead me to believe my new telescope is in fact not new, and has non-standard gears.  I haven't opened it up to verify that, though.

Is there a more plausible explanation and solution to my problem?


texts:
I have a question about purchasing another lens that's right for my situation. I own the Orion Skyquest XT10 Dobsonian, a classic case of buying a scope that is WAY to big to be carrying around everywhere, and yet I manage to get it out periodically throughout the year. I am very amateur obviously.

I enjoy using my stock 25mm but find the stock 10mm just too blurry. I do admit, I rarely get out of the neighborhood, the seeing is not great in my valley, there's city light, and I must admit I long for those hubble images popping out of my own lens.

With that said, I just feel like I should be able to get some more clarity with a new lens. I'd really like to be able to see jupiter with some more detail, right now the best I get is a small orange blur with some minor bands visible if you use your imagination.

What wouuld you recommend as the next lens in the $50-$200 dollar range that will provide a bit more detail than my 25mm but with good clarity?


texts: How close to a brown dwarf would a planet need to be to receive as much light as Earth?

texts: How close to a brown dwarf would an orbiting planet need to be in order to receive as much sunlight as Earth receives from the Sun?


texts:
Recently the news announced the discovery of a planet with characteristics similar in size to earth with the possibility for liquid water, 4.2 light years away.

Now, if there was a civilisation of human beings, pretty much identical to our own civilisation, with the same population, radio output, distribution, etc then, could we detect them now?

If not, assuming the progression of radio/telescope technology here on earth continues at the same pace, how long would it be before we were aware something artificial was happening on that planet ( disregarding communications, language, etc etc )

If it helps, assume the planet is an identical clone of earth in every way. I'm more interested in if our civilisation was on our closest star would we know?


texts: What exactly is meant by "expanding universe"?

texts: What exactly is meant when we say the universe is expanding? I understand stars and galaxies are getting farther and farther away from us, but are individual particles (atoms, molecules, anything found on Earth, etc.) drifting away from each other as well? If no, then why not? If yes, then shouldn't it, at some point, get to a point when particles can no longer bond with each other?


texts: Why are telescope mirrors made of glass?

texts:
Optical telescope mirrors are typically made from endlessly polished glass surfaces that have been aluminised to provide a very smooth surface of reflective aluminium.

But why the need for glass at all? Why can't mirrors be made of pure metal, or of metal deposited onto some other surface?

Is there something special about the glass grinding process that means no other surface can be made as smooth and still have aluminium deposited on the surface?

Or is it to do with the thermal expansive properties of the glass used?


texts:
If suddenly "knocked" or perturbed from its orbit, would gravity eventually return the Earth to its original orbit?
I am curious as to whether this is even possible.
It seems to me that since the orbit is based on gravity, the same gravity will pull it back to correct orbit eventually. Is this reasoning right?


texts: Relation between black hole mass and radius, and our universe's

texts: Is there a graph of known black holes, with their estimated mass in the X axis and their estimated radius in the Y axis? If so, where can we find it? I would like to know if a black whole with the whole estimated mass of our universe would have the estimated radius of our universe (which means our universe could be a black hole, that's why light can't escape it and it looks "finite").


texts: How to find the moons maximum culmination at a location

texts:
Forgive me if my terminology is incorrect, but is there someway or somewhere when I can calculate based on my location when the moon will be at the highest point in the sky overhead based on my location?  Per year for example?  I've been searching around the internet and haven't found a calculator or something that could do that.
For context.. I'm working on an architectural project and looking into if the moon will ever be visible through a certain skylight, even if it is for only a short period of time per year.  I'm located in Calgary, 51.0447° N, 114.0719° W
I'm currently using some parametric software to show the moons location within the 3D modeling software, but I can only input dates and get the location, not search for the highest point etc, so I can't really pin down when it will be the highest.
Thanks!


texts:
@RobJeffries' answer to What is this web on the surface of the Sun? explains why convection cells on some other stars can be far larger than they are on our Sun and includes a near-infrared VLT interferometric image of π¹ Gru from Paladini et al. 2017 as an example.

The paper says:

  For this purpose, we use the image reconstruction software SQUEEZE14, based on a Markov chain Monte Carlo (MCMC) approach to the regularized maximum likelihood problem. To assess the reliability of the image we also use a different image reconstruction algorithm, MiRa15.

Of course it's likely that the reconstruction is correct, but I'm still wondering how the possibility that the non-uniformities have arisen through some combination of instrumental and algorithmic effects have been minimized.

Question: How do they know the non-uniformities seen on the disk of π¹ Gru are real and not artifacts? For example, are there similarly generated images of stellar disks of similar angular sizes not expected to have such large convection cells that show more uniform disks?

 click for full size


texts: Mass-magnitude relation of evolved stars

texts:
In short: what mass is appropriate for absolute magnitude $M_V \sim -7$?

Some context: I'm processing the observational data (supernova light curve) and curve fitting gives me about $0.4M_\bigodot$ for ejecta mass. However, possible progenitor candidate has $M_V \sim -7$, which, I suppose, points to quite a large star. My background in astronomy is not so good (I was mostly doing theoretical physics, namely nonlinear optics and GR before I got to supernovae), so I'm doubting correctness of either my estimates or progenitor candidate parameters.


texts: Why do satellites arcs end abruptly when observed from Earth

texts:
I recently got an app that let me track the ISS. I noticed that during the time it's visible, it disappears before reaching the horizon, and sometimes reappears soon after for a bit.

Can somebody explain to me how the ISS and other satellites orbit? Specifically, what makes their visible period such a narrow one, that doesn't span all the way down to the horizon? (which is what my layman brain expected)


texts:
As we know, according to Wikipedia on Earth's inner core:

  The Earth's inner core is the Earth's innermost part and according to seismological studies, it is primarily a solid ball with a radius of about 1220 kilometers, or 760 miles (about 70% of the Moon's radius). It is believed to consist primarily of an iron–nickel alloy and to be approximately the same temperature as the surface of the Sun: approximately 5700 K (5400 °C).

Now the question is, do all planets have molten inner cores?


texts: Was the cosmic microwave background (CMB) radiation originally gamma rays?

texts: I believe that sometime after Big Bang the entire universe was filled with high energy particles. Now we fast forward to the present; most of these particles still linger and managed to avoid being absorbed, and also they lost quite a significant amount of energy and became today's "noise" which can be picked up by our TV antenna. Is this true, or am I mistaken?


texts: Could a gas giant orbit a star with a 30 year period at a distance of just 1 AU?

texts: Assuming a star with similar properties to our sun, could a gas giant orbit it with an orbital period similar to that of Saturn, but, at a much closer orbital distance, more similar to 1 AU?


texts: attractors of Mercury's spin-orbit relation

texts:
Mercury rotates at such a rate that the Sun appears to stand nearly still at perihelion, when the tide is strongest.

Is there a mechanism that tends to adjust the orbital eccentricity to improve the match – minimize the tidal torque (integrated over time), or some such?

If so, might there be other stable combinations of eccentricity and rotation coupling, other than the obvious 1:1?

EDIT: I'll rephrase, since most of you seem to think my question was something elementary like “how does Mercury rotate?” or “what the heck is tidal locking anyway?”.  I suppose it's not a bad heuristic to assume that the newcomer is completely ignorant, but I wish that assumption didn't override a literal reading of the question.

Each planet's orbital eccentricity varies over time.  Mercury's is now suspiciously near to what it would need to be for the sun to stand exactly still at perihelion.

So it's conceivable that in the dawn of time Mercury orbited at some arbitrary eccentricity and rotated at roughly 3/2, then resonance brought the rotation rate to exactly 3/2, and then something adjusted the eccentricity so that Mercury's long axis – the line of the lumps on which the tidal torque acts – tracks the sun more closely around perihelion.  (I wouldn't expect a perfect match at perihelion, because though tide is strongest then it doesn't vanish at other times!)

If that adjustment effect does happen, how does it work?

And if that happened for 3/2, could it also happen for other resonances, say 2/1 or 5/4?  For an odd denominator (other than 1) does the effect, whatever it is, behave differently (unless Mercury has a weird shape)?


texts: How do scientists know that a rock found on Earth came from Mars?

texts:
There are many documented cases of meteorites being reported as from Mars.

http://en.wikipedia.org/wiki/Allan_Hills_84001

While I can understand that it's possible to know if a rock originated as a meteorite. What I don't understand is how scientists can say it came from Mars with certainty.

How can they verify such a claim, and differentiate between a rock that is similar to one from Mars to one that really is from Mars.


texts: How much did we know about asteroids at the beginning of the 20th century?

texts:
When was the nature and size of asteroids discovered? I was under the impression that it was not until the 1980s or 1990s with deeper space probes and Hubble imagery that we learned the nature of asteroids. However, today the wonderful fortune UNIX script gave this quote from a man who died in 1910:

  Noise proves nothing. Often a hen who has merely laid an egg cackles
  as if she laid an asteroid.  -- Mark Twain

How would Samuel Langhorne Clemens have known enough about asteroids to make such a statement in the early 20th century?


texts: How well can we in principle determine $T_{\textrm{eff}}$ of a star?

texts:
This is a question about the basics of astronomy, which I have never happened to see a good discussion for. It is about how well would we be able to measure effective temperature of a star, if we had any arbitrarily perfect measurement devices.

Here is some context. Canonical definition of $T_{\textrm{eff}}$ of a star is based on its bolometric luminosity $L$ (total electromagnetic energy radiated by the star per unit time) and its photospheric radius R (radius, at which the optical depth at a given wavelength is equal to unity). This way, the definition specifies  $T_{\textrm{eff}}$ through $L=4\pi \sigma R^2 T_{\textrm{eff}}^4$, where $\sigma$ is Stefan-Boltzmann constant.

The definition clearly alludes to black-body law. Many stars, including our own Sun, have a spectrum that does not follow it. For this reason, one often talks about another effective temperature, which is the temperature of stellar material at photospheric radius, and which can be determined by examining stellar spectrum. There are a few more complications to that, but let's put them aside.

Determining  $T_{\textrm{eff}}$ is extremely important in characterising stars, therefore there exists a variety of methods of measuring it, and naturally researchers strive for obtaining the best possible precision.

Hence, the question: How well can one in principle measure $T_{\textrm{eff}}$, if one could have arbitrarily perfect instruments?

Edit: I would like to see a quantitative estimate in your answer. Is the best possible precision for $T_{\textrm{eff}}$ of order $10\textrm{K}$, or is it $1\textrm{K}$, or some $10^{-4}\textrm{K}$, or can we measure it arbitrarily well?

Here are just a few sources of uncertainty/arbitrariness: convection in stars, dependence of photospheric radius on wavelength, limb darkening, stellar variability, to name a few.

I would encourage the answers to be in the format "Source of uncertainty" - "Simple derivation" - "Estimate of the effect". If there are more than a few estimates, I will add a summary of them in the question or in a separate reply. Please, also feel free to edit the question if you might like to.


texts: How close would a Sunlike star have to be in order to be dangerous to look at it through a spyglass?

texts: Alpha Centauri A which has an about 50% higher luminosity than the Sun is obviously undangerous to look at through a handheld telescope, at about 4.4 ly distance. How close would a yellow dwarf have to be in order to make it dangerous to look at it through an average spyglass? Or to feel some heat on the eye through the spyglass? This question can also be seen reversed as "how far from the Sun would you have to be in order to look at the Sun through a spyglass without danger".


texts: What is the fastest spinning rotation of a Neutron star? I have heard that Neutron stars have a specially fast spinning rotation. What is the fastest?


texts:
I heard of one that occurred in 2008 in the Nubian Desert in Sudan, how often does it happen? Is there a catalogue of all hits or are they very rare?

Related link (This is what inspired my interest not defining what I'm looking for)
https://en.wikipedia.org/wiki/2008_TC3

At the time of asking I had not thought about the distinction between hitting the atmosphere and hitting the Earth.


texts: Does anybody recognize this kind of prism?

texts:
Supplemental to this answer to Did Edmund Scientific 4¼ inch Newtonians have 90° prisms as secondary mirrors in the 1970's? I was poking around a bit further and ran across this "1960's Edmund Scientific 'Space Conqueror', 3" reflector" with a prism diagonal at http://www.retrotechnology.com/glass/edmund.html

Question: Does anybody recognize what kind of prism this is? It doesn't look like a simple right-angle prism, but possibly something that has additional reflections and does some additional flipping or rotation.

Is there any chance that it isn't positioned correctly, it doesn't look like it is centered along the eyepiece holder's axis, but the image has a strong perspective component and we can't see the business end of the prism.


texts: How to get the longitude of the perihelion to find the Heliocentric Equatorial coordinates of a planet

texts:
I'm writing a program to randomly generate star systems and I have been having a difficult time figuring this out. I've found the equations I need to get the heliocentric equatorial coordinates, but I haven't been able to figure out how to determine the longitude of perihelion. Is it just the opposite of the longitude of the ascending node or is it a completely different variable?

It might just me, but the names for this stuff is definitely making it more confusing than it should be.

Here is all my notes:

** = power

P = planet's period

a = semi-major axis

b = semi-minor axis

M = mean anomaly

E = Eccentric anomaly

e = eccentricity of orbit

v = true anomaly

r = radial distance

A = longitude of asending node

w = longitude of perihelion

i = inclination

t = time

(r, v) = polar coordinates

(x, y, z) = Heliocentric Ecliptic coordinates

(X, Y, Z) = Heliocentric Equalorial coordinates

eccentricity

e = sqrt(1 - (b ** 2 / a ** 2))

Period

P = sqrt(a ** 3)

Kepler's Equation

M = E - e * sin(E)

Mean Anomaly
use as starting point for eccentric anomaly

M = (2 * pi * t) / P

True Anomaly

v = 2 * atan(sqrt((1 + e) / (1 - e)) * tan(E / 2))

Radial Distance

r = (a(1 - e ** 2)) / (1 + e * cos(v))

Heliocentric Ecliptic coordinates

x = r(cos(A) * cos(w + v) - sin(A) * sin(w + v) * cos(i)

y = r(sin(A) * cos(w + v) + cos(A) * sin(w + v) * cos(i)

z = r * sin(w + v) * sin(i)

Heliocentric Equalorial coordinates

X = x

Y = y * cos(i) - z * sin(i)

Z = y * sin(i) + z * cos(i)


texts: Can the Keck Observatory be improved with a third telescope?

texts: Can the Keck Observatory resolution be improved by adding a third telescope? I imagine that that would be cheaper than building a completely new telescope?


texts:
I am looking into getting a zoom eyepiece for myself, and not sure on what basis to evaluate and compare various options.
For some background on the type of observing I plan to do see my earlier question: Good eyepieces for Saturn and Jupiter
Here are some examples of zoom eyepieces that I've looked at so far

Astromania 1.25" 7-21mm Zoom Eyepiece Apparent field of view is 30- degree at 21mm and 43- degree at 7mm
Meoptex 1.25"-7-21mm Zoom Eyepiece No further information

On these pages there are links to several more options.
It would be a very great help if anyone could help me figure out on what basis I might choose one of these or quickly rule some out, or recommend how I could search for more options.


texts: How are heavier elements such as carbon and silicon distributed within the Sun?

texts:
In a previous question I asked about the source of carbon and silicate dust that Solar Probe Plus will encounter in its close flyby of the Sun. It seems likely that most sources would include infall from outside the solar system or fragments resulting from collisions inside the solar system.

But the Sun is believed to be about 0.4% carbon and 0.1% silicon by mass (see  here and here). I believe these represent the relative abundances during the formation of the Sun, but do not account for nucleosynthesis that early in the Sun's life.

Is the distribution of carbon and silicon in the Sun is believed to be uniform, or does it have a radially dependent distribution? Is there be any kind of gravitational settling, i.e. heavier atoms tending to move toward the center as happens in planets?

Since we can only directly measure elemental abundances directly near the surface using spectroscopic techniques, would the radial distribution come from some model or calculation?


texts: Can virtual particles be the source of dark matter and dark energy?

texts: I had this question for a long time. But otherwise the question basically sums the whole thing up.


texts: Astronomy detective question: what part of the sky are these photos of? What are a few of the stars?

texts:
The 9to5Google article Exclusive: Official Pixel 4 camera samples show astrophotography, selfies, more [Gallery] shows some surprisingly nice (at least to me) photos of the Milky Way.

I've asked Milky Way with a cell phone, how is this possible? in Photography SE, but here I'd like to double check the scale and FOV of these images.

I'd like to establish the FOV and scale in pixels per degree for these images, so I need to know what part of the sky are these photos of and what are a few of the stars? I understand that a wide field view with a cell phone camera may have some distortion so I'll do the corners separately from the center.

I wanted to ask for an estimate of the latitude. I guess that's only possible if we assume the bottom edge is parallel to the horizon.

click for full size:


texts: Pretty sure Quasars were involved in increasing Galactic metallicity but is there evidence of quasar AGN's generating heavy elements, such as radioactive ones and shooting them across the universe in the relativistic jets? If there's no evidence is it theoretically possible?


texts: Possible Reason for the "NASA UFO sighting: Alien ship 25 TIMES size of Earth spotted near the Sun" news (does it fake or ...?)

texts:
I have this news:
NASA UFO sighting: Alien ship 25 TIMES size of Earth spotted near the Sun
and tried to find the NASA site link by this link, but not found that news , so like to know what could be the reason of this situation, does it fake?
Thanks.


texts:
I've been reading and thinking about this subject for some time, but I can't seem to find a clear answer.

After reading Q14:

  Aspects of the Higgs boson suggest that our Universe is only
  “marginally stable,” or is perhaps in a transition phase to a more
  stable state that would result in a universe with fundamentally
  different properties.

And this article:

  With the discovery of the Higgs field, one question we can ask is
  whether the Universe as a quantum system it is in a stable, low-energy
  state, or in a metastable higher energy state?

According to the standard model of particle physics, the answer depends upon the masses of the top quark and the Higgs boson. The more massive the Higgs boson, the more likely the Universe is to be stable. The more massive the top quark, the more likely the Universe is to be metastable, or even unstable. From our current measurements of the top and Higgs masses, it seems that our Universe is metastable.

Maybe an answer already been found, but I just didn't find it, or am I not on the right level.

Is our universe stable or metastable?


texts: Earlier this morning when I went outside to get a drink around 04:00 Tasmanian time (GMT +11), I saw a line of moving lights in the night sky. They were all moving at the same speed similar distances from one another in straight line apart from the last two that were more spread out and out of line. There was around 20-25 of them although I couldn't get a final count as I couldn't be certain there more at the start of the line that had gone past my sightline. They all moved and looked like satellites so it's possible it's some sort of strange cluster I don't know about.


texts: How do we know how fast the surface of a neutron star is rotating?

texts:
I understand that we can count pulses in time, but how do we know that the magnetosphere is rotating along with the surface of a neutron star?

Can we measure the rotation of a neutron star in any other way like red-blue shifts? It should be pretty difficult due to the small radius and big distance but is it possible? Is it already done?


texts: Star rising times in a different place given the latitude and time of one place

texts:
I don't know astronomy that well, but I am preparing for the second stage of IJSO, and here in India they do add some questions like these ones.

  A star is seen rising from Kolkata (23.5N 92 E) at 7 pm IST. What time can it be seen rising from Mumbai (19N 72E)?

If someone could explain how I might go about solving this, and some surrounding theory so I can grasp the concept, I'll be really grateful.


texts:
Despite the revolution of the earth around the sun, why does the Polestar appear to be at the same place all through the year?
My daughter, a class 8 student, asked me this question.


texts: Does the Canis Major Dwarf Galaxy have a black hole at its centre?

texts: I am just wondering: is there a potential galactic centre out there that's very close to us? I know that CMDG is irregular, but can it still contain a black hole at the centre?


texts: Orbiting and landing on non-sperical objects

texts:
If we orbit a non-spherical asteroid or moon at a sufficient distance I believe that we can consider it to be a point mass. Therefore we can take up a conventional orbit.

Assuming our lander craft is of insignificant mass compared with the body we wish to orbit and land on, how do we cope when we get near to the surface?

Presumably an orbit will become more and more chaotic the nearer we get. As we try to land, unless we somehow synchronise with the body's rotation things will be equally tricky.

What implications did this have for Rosetta's Philae and what implications will it have for much larger and maybe more irregular bodies?

Is there some rule-of-thumb method to get an approximate answer or do spacecraft simply have to make minute by minute adjustments?

Note

I understand mathematics to a reasonable level but really I'm more interested in the practicalities of such landings. To what extent can they be pre-calculated and to what extent must they be adjusted on the fly.


texts: Time after sunset until star can be seen

texts:
Given a star's apparent location and apparent magnitude, how how many degrees below the horizon must the sun be for the star to be visible to the naked eye for an observer on Earth at a specified location and elevation? You can ignore all light pollution, though I understand there will be some error due to air quality/weather/atmospheric aberrations.

Is there such a formula? If not, why not and what methods of approximation are available?

(I figure the brightness of the afterglow of the sun at a certain angle above the western horizon can be calculated for a certain time and place, and if it is less than the apparent brightness of the star in question, the star will be able to be seen.)


texts: Are sunspots vertically displaced from the surrounding photospheric plasma?

texts:
While reading a paper on the helioseismology of sunspots (Cameron, et al.), very brief reference is made to the "vertical displacement of a blob of plasma." This caused me to wonder if the emissive surface of the sunspot itself were perhaps depressed from the remainder of the photosphere. If this does occur, is there any literature on mechanisms? I would be very interested to learn more. There was one paper I came across around formation of sunspots from a toroidal field (Parker); but, it seemed to focus more on the vertical displacement of magnetic field lines rather than the plasma itself.

Thanks.


texts: How big can an object get before its core becomes degenerate?

texts: I am wondering, what is the most massive object we know of that does not have a degenerate core, and what is the least massive object that does have a degenerate code? We know that Jupiter has a core that is obviously degenerate. A quick Google search shows that Saturn is indeed degenerate, and is on the low end of electron-degeneracy. Are there any lesser-mass degenerate objects there, and what is the approximate boundary for electron-degenerate and non-degenerate matter?


texts: How is magnetic field is generated over the sun?

texts: Dynamo theory suggest how magnetic field generated on Earth. Due to flowing magma which contains molten iron generates magnetic field on earth. But how magnetic field is generated over sun?


texts: Is Venus in some way tidally locked to... Earth?

texts:
The video here demonstrates how Earth sees the same face of Venus every inferior conjunction (i.e., two planets are the closest to each other):

https://www.youtube.com/watch?v=4m_ouMC61-w (or https://twitter.com/physicsJ/status/1263402883275386880)

This might be caused by some kind of tidal locking, or it might be a coincidence. Does this type of gravitational resonance exist, either in theory or in the wild (e.g., between moons of Jupiter or Saturn)?


texts: Can we create neutron star by pressing earth? Or other objects?

texts:
Everywhere I can hear, that if we press anything to the right size, we create black hole.

Can we create neutron star by pressing, for example, our planet? And what if we press something bigger, like Jupiter?


texts: How much are Neptune's and Uranus' orbits perturbed by Pluto and other KBOs?

texts:
Reading another question, I came across the argument that inconsistencies in Neptune's and Uranus' orbits lead to the discovery of Pluto.  This brief write-up mentions Percival Lowell and William H. Pickering by name as two people who looked for the theoretical 9th planet.

My question is, were inconsistencies in Neptune's and Uranus' orbits detectable by early 20th century methods or were these scientists just chasing calculation or estimation errors with dreams of finding the next planet.  My (guess) is that Pluto is much too small, and too far away and just one of many similar mass kuiperbelt objects, so it's unlikely that it was really discovered by measured inconsistency in Uranus/Neptune orbits method, (despite the fact that there are articles that say that's precisely how Pluto was discovered).

In a nutshell, that's the question.  Was the wobble that Pluto's causes on Neptune's orbit observable by 1910-1930 observation methods.  And related, was the wobble that the entire kuiperbelt (some 20 to 50 times the mass of little pluto, but much more spread out), was that wobble detectible by 1910-1930 methods.

Hard math isn't necessary to me for an answer, as I find the math hard to follow sometimes, so feel free to answer with or without mathematical calculations.


texts:
Last evening I assisted in an interesting phenomenon in my region (Eastern Europe). It was a dark sky with heavy rain and blinding lightning (which struck every 5 seconds or so), but NO thunder at all.
I was thinking that the explanation might be:

The clouds are very high in the sky and and the sound does not reach the land
The wind deviated the sound somewhere else.
It was not a storm and aliens were conducting an experiment in the atmosphere

I'm not a meteorologist, so if you have a better explanation, please let me know it.


texts:
I'm from the Philippines, this is the first time I've seen such a bright star. I don't normally see stars at all cause of my poor eyesight but this star is very bright and really noticeable.

I took the first picture around 4:45 am, then now the little white which is still the star. The second I took it around 5:15 am when the sun already rising. The star and the sun are both in my east. The star is like going up while the sun is rising.


texts: I read about Tachyons and Gravitational Waves and also about Exotic matter, really nothing can escape a Black Hole, can Axions escape for providing a new hope?


texts: Why telescope mirror glass shipped as randomly broken chunks of a constant size in cardboard boxes?

texts:
The video MIRROR LAB: Preparing for Casting GMT's Mirror 6 shows the unpacking several hundred boxes full of broken glass from OHARA, packed in styrofoam.
The glass chunks are a fairly uniform size of perhaps 15 cm, and of compact shape; there are no long slivers or sheets; they are all very roughly cuboids.
This seems to be deliberate. It could have been ground to a finer, pourable size, or even smaller for filling the nooks and crannies of the support web at the bottom of the mold, or in much larger sheets or bars. But these roughly block shaped pieces are stacked like bricks by hand, one at a time, into the mold.
Why is this so?

more screen shots (in case video disappears) click for full size:


texts: How can Mercury's sodium tail be imaged?

texts: I recently learned that Mercury has a sodium tail. Can this sodium tail be imaged with a ground based telescope? Is so, what is the minimum setup required to be able to take a picture of it? Do you need any specific filters?


texts: If it only takes 8 minutes for that light to reach the Earth, what took up most of the time?

texts: If it only takes 8 minutes for that light to reach the Earth, what took up most of all that time to get to the Earth?


texts: How to show that the Jeans Criterion for Mass, Radius and Density are equivalent?

texts:
The gravitational collapse of a gas cloud can be described by the Jeans Criterion for mass, radius and density of the gas cloud, which is (c stands for cloud):

$$M_J = (\frac{5kT}{G \mu m_H})^{3/2} (\frac{3}{4 \pi \rho_c}) ^{1/2} $$

$$R_J = (\frac{15kT}{4 \pi G \mu m_H \rho_c})^{1/2} $$

$$\rho_J = (\frac{3}{4 \pi M_c^2}) (\frac{5kT}{G \mu m_H}) ^{3}$$

I wanted to show that they are equivalent and simply used

$$\rho = \frac{m}{V} $$

on the criteria above an rearranged the equation.

However this doesn't work. What am I doing wrong?

Thank you for your help!


texts:
given that everyone wonders whether there is a chance that there is something to oumuamua that is not natural, what about tumbling (and/or aiming?)?

is there a natural gravitational or other force that would naturally stabilize non-orbiting asteroids in space?

I would guess that there is a chance that we could detect tumbling.


texts: What would happen if we released water into deep space?

texts: If we went to deep space by a spacecraft and released water into space, what would happen? Would the water freeze to ice or would it remain as a liquid?


texts: Do other supercluster like Laniakea also get pulled by the Great Attractor?

texts:
I'm not sure, whether there is any other observable super cluster like our local one, Laniakea, and if they do exists, do they also get pulled by the Great Attractor?

I am a little confused about superclusters and The Great Attractor, how they do exists relative to each other and how we can see/know from our galaxy, specifically from the Earth.


texts:
I've hear several theories stating that the universe is expanding faster than the speed of light, others claim that the universe expands faster the further away you measure it. Which of this is correct and how do you prove it (mathematically)? Furthermore, does this correctly imply, then, that eventually galaxies will be so far away, and moving so fast, that we will never see them again?

Thank you in advance!


texts: What is the first recorded reference to the Moon being a satellite of the Earth?

texts:
I saw a list recently of the moons of the various planets and the discoverer(s) and date of discovery. Earth's Moon was listed as Unknown.

I know you don't 'discover' a huge disc in the sky. But still, what is the first recorded reference to the Moon being a satellite of the Earth? That someone knew it is smaller and orbiting? Celestial Sphere does not count.


texts: Does Celestia respect 'setframe' coordinate systems?

texts:
Through trial and error (see script below that summarizes what I've found), I've learned Celestia's coordinate system appears to be:

The x axis points to the vernal equinox
The y axis points to the ecliptic north pole
The z axis points to 18 hours right ascension, -23.4393 declination (ie, the obliquity of the ecliptic)

regardless of whether you choose the "equatorial", "ecliptical", or "universal" frames.

I wrote the script below to confirm this: regardless of which setframe command you uncomment (or if you leave them all commented), the results are the same.

{

# using Celestia 1.6.1

# set to equatorial frame
# setframe {ref "Sol/Earth" coordsys "equatorial"}
# setframe {ref "Sol/Earth" coordsys "ecliptical"}
# setframe {ref "Sol/Earth" coordsys "universal"}

# 27 Psc is near the vernal equinox at a distance of 234.48 ly
# this brings me within 14 ly
setposition {base [234.48 0 0]}
select {object "27 Psc"}
center {time 0.01}
wait {duration 3.0}

# 42 Dra is near the north ecliptic pole at 18h, 66.56 declination
# this brings me within 15 ly
setposition {base [0 314.82 0]}
select {object "42 Dra"}
center {time 0.01}
wait {duration 3.0}

# 7 Sgr is near the 18h, -23.4393 declination
# this brings me within 20 ly
setposition {base [0 0 1079.99]}
select {object "7 Sgr"}
center {time 0.01}
wait {duration 3.0}

}

I am aware that https://en.wikibooks.org/wiki/Celestia/Binary_Star_File suggests the coordinates are stored internally as some gyration of ecliptical coordinates, but assumed "setframe" would change this.


texts: Is a black hole a three-dimensional or four-dimensional object?

texts: Is a black hole a three dimensional or four-dimensional hole?


texts: Why is liquid water considered a requirement for life?

texts: I`ve heard about different extremofiles living on earth. Is water a requirement for life because we have not seen life survive on earth without it, is it a chemical  reason which makes life without water seem impossible? Could life exist with water, but in gas form? What makes the liquid part so important? Can life be based on other  liquids on potential exoplanets?


texts: How to see other celestial things using stars for direction?

texts: I have a simple question. I can see orion constellation clearly in the night sky. I read it somewhere on this website that gemini is on the left-hand side of orion constellation. I was able to spot gemini later that night. I was wondering on how to spot other constellations using orion and gemini constellation.


texts: Why are there optical differences between sunrise and sunset?

texts:
I've noticed that sunrises are not reverse sunsets regarding the sky hues and lighting.

Sunrises always start pinkish and end with a glorious yellow sunshine.
On the other hand as the sun sets lighting gets orange and the sky gets a hellish red colour. I've noticed this many times regardless the weather or temperture.

Why is this contrast between colors (pastel-like in the morning vs vivid in the evening) in a fenomenon that should be same in both instances in a day ?

Am I the only one that perceives this difference ?


texts: Can dark matter decrease the Jeans length?

texts:
I am wondering if there are any models of interstellar cloud collapse out there which take dark matter into account.

If dark matter has local perturbations or density fluctuations, then that may be a large enough effect to cause collapse of an interstellar cloud. This might increase the mass and density of a cloud enough to overcome the kinetic energy of hydrogen atoms leading to collapse.

Are there dark matter density variations at the scale of interstellar clouds?


texts: What would an asteroid inside of Mercury's orbit be called?

texts:
The first Vatira asteroid has been discovered. This makes me wonder if there is already a name for the hypothetical class of asteroids that orbit entirely inside of Mercury's orbit. It wouldn't be the first time that an astronomical class is named before being actually observed.

Is there a name to designate the hypothetical subclass of Atira asteroids whose aphelion is closer to the Sun than Mercury's perihelion ?


texts: I was wondering about a planet who orbits two stars. Could it be that it moves as in the image?


texts: What is the level of tidal heating between bodies that are already in mutual tidal lock?

texts:
As I understood tidal heating, it comes from tidal force acting upon a body as it spins, distorting it; the wave of distortion travels along the surface (along with apparent travel of the other body on the sky) and continued friction as the matter is strained into the traveling wave is the source of tidal heating.

Now, if the two bodies are in a tidal lock, the distortion remains constant - it doesn't move. There's no new work done as the bodies remain immobile relative to each other. The tidal heating should be a flat zero.

Meanwhile, Io has immense volcanic activity attributed to tidal heating - despite it being tidally locked to Jupiter. While it still heats Jupiter, dragging its own tidal wave around it, Jupiter shouldn't contribute any heat to Io as its distortion remains constant over time, a stable equilibrium.

Is that just residual heat from times when Io was spinning or am I missing something?


texts: How do different formulas for calculating the mean anomaly of an elliptic orbit correlate?

texts:
I need to calculate the mean anomaly of an elliptic orbit at a specific point in time. I found two different formulas for $M(t)$ and I'd like to know how they correlate and if they result in different ouputs.
The first formular is:
$M(t) = \frac{2 \: \pi}{T}\:(t-t_o)$
and its taken from this book.
The second formular is:
$M(t) = M_0 + \Delta t \sqrt{\frac{\mu}{a^3}}$
taken from this document.
Inputs:
$T$... Orbital Period
$t_o$... Starting point in time (epoch)
$t$... Point in time
$\Delta t$... Elasped time: $t-t_0$
$\mu$... Standard gravitational parameter $\mu=GM$
$a$... Semi-major axis
$M_0$... Mean anomaly at epoch


texts: Why nobody cares to give the nearest stars better names?

texts:
The star occupying 6th place on Wikipedia's list of nearest stars and brown dwarfs can be called either Lalande 21185, BD+36 2147, Gliese 411 or HD 95735. That seems to me like a fine, quadruple choice of equally bad names.

I mean, I know these come from positions held in various star catalogues and maybe aren't that bad compared to monstrosities like WISE J085510.83−071442.5, but can't we keep those for stars like 50 light yrs away and invent something better for our nearest neighbours?

This year we saw a batch of confirmations for planets orbiting in habitable zones of many of these stars. In not so distant future we may find ourselves discussing possibility of sending probes to some of these systems. Aren't better names long overdue?


texts: How bright are geostationary satellites due to reflected sunlight?

texts:
We are all familiar with seeing low-Earth orbit satellites scooting across the sky in a couple of minutes. Many of them are bright and readily identifiable with the naked eye. Geostationary satellites on the other hand are much further away and would remain fixed in position (though moving very slowly with respect to the background stars).
How bright are geostationary satellites in reflected sunlight? Can any of them be spotted, even with a telescope?
Related questions:
How will Starlink affect observational astronomy?
How do satellites impede current telescopes?


texts: I am currently living in Bangkok and I love astronomy. However, I haven't been able to find an official astronomy exam that I can do to gain college credit. Could someone help me out please?


texts:
A Nebula has bright awesome colors that include red, blue, green, orange, white, etc?

They're result of excitation of electrons.

Is there a clear explanation as to which color is attributed to an atom for Color properties in Cosmos!?


texts: Question on Friedman equation involving cosmological constant

texts:
This is the question:

By considering both the Friedmann and acceleration equations, and assuming a pressureless
Universe, demonstrate that in order to have a static Universe we must have
a closed Universe with a positive vacuum energy. Using either physical arguments
or mathematics, demonstrate that this solution must be unstable.

I started off with the friedmann equation and equated H^2=0 and K>0. How to proceed further and prove that lamda is positive?


texts: Since Jupiter is the biggest planet in our solar system and is made up of mostly hydrogen and helium, (the gases the Sun uses to create energy), how come it didn't form as far out as say Uranus or Neptune since when our star formed it took most of the gases around it to create? Just a little confused on this, thanks for the help!


texts: Can the martian dichotomy (SIH) and the moon's formation (GIH) be related?

texts:
If we assume that the Single Impact Hypothesis regarding the martian dichotomy (wikipedia) and the Giant Impact Hypothesis regarding the Moon's formation (wikipedia) are true, then is it possible that these two events were related?

Here, by related I mean that they were not independent from one another.


texts: "Who saw" the binary neutron star merger first? What was the sequence of events? (GRB/GW170817)

texts:
I'm trying to read Multi-messenger Observations of a Binary Neutron Star Merger the "cast of thousands" OPEN Access ApJ letter 848:L12 (59pp), 2017 October 20 https://doi.org/10.3847/2041-8213/aa91c9 and get a feeling for the sequence of events that took place as the gravitational waves and gamma ray burst reached Earth at about 12:41 UTC 2017-Aug-17.

There seems to be five instruments involved in the first detection and direction determination; LIGO-Hanford and LIGO-Livingston, VIRGO, Fermi-GBM, and INTEGRAL. The first three are gravitational wave detectors and the last two are gamma-ray telescopes in Earth orbit. Figure 2 of the paper (part of which is shown below) provides a densely packed infographic of the early observations. In the top left one can see an inset that spans from twelve seconds before the merger during the gravitational wave (GW) ramp in frequency, to six seconds after, where the majority of the gamma ray burst (GRB) is detected.

Somehow the combination of the GW and GRB set in motion a sequence of events that triggered a world-wide observation campaign to look for the event in all the remaining electromagnetic spectrum from radio through visible and UV to X-rays. Neutrino data streams were checked as well.

Question: I'd like to ask about the sequence of events, the alerts, and the rapid automatic and manual analysis of the GW and GRB data which triggered the alerts. Which detector or combination first "saw" the event as some kind of flagged event? Did one trigger a rapid analysis of the other? Were these automated alerts triggering software to re-analyze, or SMS text messages to thousands of cell phones triggering everyone to sit down at their work stations?

below: Figure 2 (partial) showing the timeline seconds before and hours and days after (logarithmic scale). The GW and GRB data were used (see Figure 1) to start the search for the rest of the electromagnetic search.

below: Figure 1 showing the localizations made from different sets of GW and GRB detectors.


texts: Calculate Global (ECEF) coordinates of Observer

texts:
I have the local coordinates of satellite and global coordinates of satellites. I want to calculate the observer position in global (ECEF) system.
How can I do this?

I also explain this question with more steps in following link.
https://gis.stackexchange.com/questions/383255/local-system-to-lat-lon
I am missing something, Can you please help me where I went wrong?


texts:
astrosnapper@'s thorough answer to the question What is precipitable water vapor in millimeter-wave radioastronomy and how is it measured? links to the paper Observing Conditions for Submillimeter Astronomy which discusses spectral windows of atmospheric transmission in the 100 ~ 1500 GHz range. These windows are "delineated" or limited by strong absorption lines of molecular water vapor in the atmosphere.

Figure 2 is shown below. The caption reads

  Fig. 2. Energy levels of the lowest rotational states of water with transitions labeled by the frequency in GHz. The lines at 557, 752, 988, 1113, and 1229 GHz delineate the principal submillimeter windows.

and displays ortho- and para- water separately.

Curious to find out what those were, I went to Martin Chapin's (also here) site Water Structure and Science which discusses the physics of ortho- and para- water, and describes experiments on single water molecules trapped and isolated in C60 fullerene "cages" (Endohedral fullerenes):

ortho-Water and para-Water

Question: Have caged molecules ever been observed in space?

These could be trapped in fullerenes (which I believe have been observed) or otherwise.


texts: How do comets and other solar system bodies gain energy to exit the solar system?

texts: I recently learnt that some comets like C/1980 E1 (Bowell) interacted with objects like gas giants in the solar system and gained enough energy to exit the solar system. But from Physics, I know that only if the total mechanical energy of a body is positive, can the body exit the solar system. An interaction with a gas giant should merely convert some of the potential energy of the body to kinetic energy and the total energy of the body should remain unchanged. If so, how can such bodies achieve positive mechanical energy to exit the solar system?


texts: How should I find a telescope for research time?

texts: I'm an undergrad in physics and astronomy deciding to look into applying for time on a research telescope, and I'm not sure how to proceed with locating/finding telescopes that I can apply for time on. Specifically, I'm interested in looking at the chemical composition of protostellar disk(s). Any applicable information would be nice.


texts: Why can't we observe the Oort cloud with a telescope?

texts:
The Oort cloud is a hypothetical structure based on our observation of long-period comets. There are currently proposals to design probes to confirm the existence of the Oort cloud.

Now, sending a probe would have other benefits, but why can't we observe the Oort cloud with a telescope?


texts:
eLisa - Evolved Laser Interferometer Space Antenna.

  A LISA-like mission is designed to directly observe gravitational waves, which are distortions of space-time travelling at the speed of light. Passing gravitational waves alternately squeeze and stretch objects by a tiny amount. Gravitational waves are caused by energetic events in the universe and, unlike any other radiation, can pass unhindered by intervening mass. Launching eLISA will add a new sense to scientists' perception of the universe and enable them to listen to a world that is invisible in normal light.

The "duh" answer to my question is "Gravity waves, of course."

Obviously this is not what I'm asking.

So, we've deployed eLISA and we spotted a gravitational wave passing. Well, there went the wave. What data do we extract from it? What discoveries, observations will we acquire? What else can we discover with it than "there was a gravity wave, and it came from this direction"?


texts: Mathamatica vs Sympy and Astropy to solve basic astronomy problems: solving linear equations and unit conversion

texts:
I realize this may be slightly off topic, but I also believe this is probably the best way to get an answer to my question:
What is the best combination of software packages / programming languages to solve basic astronomy questions, such as applying Kepler's laws, calculating radial velocities (i.e. basic linear algebra) etc in a scalable way?
Essentially what I need is

Equation solver (Mathematica or Astropy combined with Sympy?)
Unit conversion (Mathematica and Astropy)

I'd like to hear some opinions what combination of tools people are using to perform basic astronomy calculations such as the above example, where unit-conversion and solving linear equations appear to be the most common tasks.
As an example problem:
How would I solve for a variable in kepler's third law after assigning values to all other variables?
a^3/P^2 = G * (Ms + Mp) / 4 * pi^2
It seems simple in Mathematica doing Solve[a^3/P^2 == (G (Ms + Mp))/(4 \[Pi]^2), P]]. Is there any equivalent in python that can solve and at the same time handle units?


texts:
Where does the energy from a supernova come from?

My understanding is that the iron core collapses into a large ball of neutrons - is that effectively a star-sized nuclear explosion? What is the reaction product called?

Why does the effect go supercritical, instead of finding some equilibrium rate of burn? I've read discussion that the reaction energy does not appear to be enough to explain the energy seen in a supernova? How big is the gap?


texts: Why does Newtonian physics give the right radius for a black hole?

texts:
When computing the distance at which the escape velocity is equal to the speed of light, the result is equal to the Schwarzschild radius. Is this just a coincidence, or is there a physical reason why the Newtonian approximation give the correct result?

If this is not a coincidence, then why is it OK to use Newtonian physics here?


texts: Why is right ascension measured in hours?

texts: When viewing star maps in Stellarium, I noticed that the meridians of the equatorial grid were denoted in hours and not degrees, and that always puzzled me. Why did astronomers choose this system? I understand it has something to do with being relative to the Earth's rotation which takes 24 hours, but I can't figure out exactly what.


texts: What record do we have of the length of supernovas?

texts:
recently I heard an astronomer on the radio claim that the supernova we have observed in our own galaxy lasted about 6 months, while in distant galaxies they last about 7-8 months, due to relativity and the expanding universe. He didn't give any references. Just to be clear, I don't mean to imply that he implied the actual duration was different, but that it only appeared different because of expansion.

I've found records of supernova, but only 1 mentioned how long it lasted, the first recorded one was said to last 8 months according to wikipedia.
Can someone point me to a list that contains both the location and duration of supernova's .


texts: Is it possible that absolute magnitude for two stars is equal for some wavelength?

texts:
The title explains the questions. I don't find any problem with it. As If the two stars A and B do have equal absolute magnitude for some wavelength $\lambda_0$ then
$$M_A=M_B$$
$$-5(\log d_A-1)+m_A=-5(\log d_B-1)+m_B$$
$$m_A-m_B=5\log\left(\frac{d_A}{d_B}\right)$$
I don't find any problem with this. But I'm not sure if this is true. Can any help me with this?


texts: if the universe is infinite shouldn't it have experienced an infinite number of universe ending events?

texts: or is it that the definition of infinity used here excludes such events like there are an infinite number of odd numbers but 2 isn't in that set?


texts: What is "class 4 light pollution" and could I estimate my own area's class visually?

texts:
This question currently asks

  I am living in the northern hemisphere in Greece and in class 4 area (light pollution scale).Is it possible to see the Andromeda galaxy with a naked eye?

I'd never heard of a light pollution scale before. How does the scale work, and if I wanted to gauge or estimate my own area, can I do that by looking at objects in they sky visually?


texts: Have any more "white dwarf pulsars" been discovered or searched for?

texts:
Back in 2016, Marsh et al. reported that the binary system AR Scorpii exhibits complex radio signals similar to those observed from traditional pulsars. In particular, pulsed synchrotron emission appears to be produced by interactions between the magnetospheres of a white dwarf and a red dwarf, powered in part by the spin-down of the white dwarf. The system has been dubbed the first "white dwarf pulsar" based on the signals.

The system is thought to be similar to, if not an extreme case of, intermediate polars; we know of a number of these systems. Therefore, I'm wondering: Have there been any concerted searches for other intermediate polars exhibiting this pulsed emission, and if so, have any candidates been discovered (possibly serendipitously)?

This is partly belatedly in honor of February's focus tag.


texts: Is there any way a planet could form independent of a star?

texts: I just recently heard that there are currently no theoretical models that support planet formation without a star, but I can't remember where. So, I thought I would request all of your expertises. Thank you much. I wanted to confirm whether this is true or not and to know if there are any theories that could account for planet formation in interstellar or intergalactic space.


texts: When did scientists discover that the Sun has a life cycle and that it is going to die?

texts:
I have been researching the history of scientific studies about the the Sun. However I have been unable to find out much information about how the scientific consensus started forming around stars' life cycles.
I know that it has been known since Galileo that some star have sudden changes in luminosity during their life. But I was unable to find out when scientists actually discovered that stars are born and die, and especially how this influenced the view on the future of the Solar System.
I suppose this happened somewhere at the start of the 20th century, when more information and research about supernovae was being found, but I couldn't find more precise information about it.
Any more precise information about this is greatly appreciated.


texts: Will the TESS telescope be much better than the Kepler telescope?

texts:
I would like to know please whether or not the TESS telescope will be much better than the Kepler one.

Thanks.


texts:
I have seen a large circular formation of cloud around the full moon sometimes.

Have anyone seen the same? What is the reason behind this formation?
Due to lunar attraction?

Most of the sky is empty and clear, and no clouds at all, only around the moon, far from the moon, not just very close, that cloud circle formed.
I saw this many times, like the below drawing:


texts: Why are perihelion and the shortest day in the northern hemisphere different?

texts: The orbit of Earth is elliptical and the nearest distance to sun is perihelion position. Should it not be the shortest day in the northern hemisphere?


texts: How can I find the width of an orbit knowing some values?

texts: I need to find the width/x-radius of an orbit, which is ellipse shaped, knowing variables like the orbit's length(perihelion + aphelion in this case) and the eccentricity. I am not sure if this is even possible, I am pretty new to this. If there is already available data on this that you're aware of, it would solve my problem too.


texts: What would people on Earth see during a close comet pass?

texts: What would people, standing on Earth, see, hear and smell, if a short period comet, with a two mile diameter nucleus, came by at 100,000 miles above us?


texts: Is remote measurement of isotope ratios possible, or must a sample be aquired

texts: Is it possible to measure to measure isotopic abundance of remote astronomical objects - ie measurement without having a sample to feed into a mass spectrometer? Do different isotopes show any differences in absorption or emission spectra which can be used for this purpose?


texts:
The LOFAR project open a new window in the universe's study because it allows to receive low frequences of the universe that we could not get because of the ionosphere.
But I'm wondering how can LOFAR pass through the ionosphere? Is it because of the large fields of antennas? Or it is something else?
Thanks for any answers which can clear my mind.


texts: Is TDB monotonic? Does it or any of its derivatives have yearly discontinuities with respect to an atomic clock?

texts:
This in-depth answer mentions that

  ...TDB is updated every year. As technology improves, these subtle updates change the timing of past events.

This makes me wonder...

Does this updating result in yearly discontinuities in TDB relative to a smoothly-running (non-discontinuous) atomic clock?
If not, does it result in discontinuities in the first derivative of the difference?
Is TDB ever non-monotonic?


texts: How to Calculate Planetary Equilibrium Temperature in Binary systems

texts:
I'm working on a program that generates the basics stats of a terrestrial planets in binary star systems. I'm not the best at this kind of math, so I'm having trouble calculating the planetary equilibrium temperature.

The formula I'm currently referencing was posted in a thread from almost 4 years ago: How to calculate the expected surface temperature of a planet.

It seems reasonably accurate since (if memory serves me) using it yields a good answer for Earth and Mars. However this is for a system with one radiating body not a system with two radiating bodies (binary stars).

My instinct is to treat the two stars as one big star and add the wattage $(w/m^2)$ the planet receives from the various stars. So total watts = watts star 1 + watts star 2. That seems reasonable to me, at least for the purposes of calculating planetary temperatures.

I've already done work to calculate the watts received by the planets from the various sources. I've used this equation, subbing in values for both stars.

$$
F(L/S^2)
$$

L = Luminosity (in fraction of Solar), stars 1 & 2 (respectively): 0.0159 & 0.7758
S = Semimajor Axis (in AU), stars 1 & 2 (respectively): 0.1228 & 3.6000
F = Earth Mean Solar Flux $(w/m^2)$ 1362

So the above calculation yields a Mean Solar Flux for the example planet of $1344w/m^2$ from Star 1 and $92w/m^2$ from Star 2. Adding those together I get a mean global wattage of $1436w/m^2$.

However, I'm unsure how to modify the original equation to utilize the above calculate solar flux (ideally without having to reference the original luminosity and semimajor axis variables). What is the correct way to alter the formula?

Any help would be very much appreciated!


texts: How can there be 1,000 stellar ancestors before our Sun?

texts:
I've heard from a few sources* recently that the Sun is a 1,000th generation star, meaning it had a thousand stars that came before it based on its heavy-element content.

I understand that earlier stars' supernovae created the heavier elements and those were incorporated into the Sun when it formed and we can calculate the generation based on that.

My question is based on the age of the universe and the age of the Sun and the average age of stars in the galaxy.

Basically, the universe is ~13.7 billion years old, the sun is ~4.6 billion years old (and has ~5 billion years of life left), which means it was formed when the universe was ~9.1 billion years old.

For 1,000 stars to live in that span of time, those stars would have to have an average lifespan of ~9 million years (not including time between stars). This equates to each of those thousand stars having an average mass of ~100-150 solar masses so their lives would be sufficiently short to not go over that ~9 million-year lifetime.

So basically, there were 1,000 stars that lived and died before our Sun, all of which were huge monsters. This just all seems so improbable. How can this be?

* TV shows, I don't remember which ones


texts: How do you mount these binoculars and telescope on this tripod?

texts:
Have this telescope and tripod that is missing the 'tripod head platform' to mount to a binoculars or telescope. Can I buy it somewhere? [Photos attached]

I would like to connect the tripod to the D70 telescope, and also this Celestron binoculars that comes with a tripod mount piece that has two screws in it, you could see in the picture on the right of the binoculars.

EDIT: added additional photos

Photos from the Celestron manual, showing the tripod with all parts:

My tripod, missing the tripod head:

Telescope:


texts: How do disk-shaped galaxies then form at the sites of spherical galactic halos? Do the halo stars start orbiting or just sit in place?

texts:
Phys.org's Astronomers detect large amounts of oxygen in ancient star's atmosphere mentions

"Stars like J0815+4729 are referred to as halo stars," explained UC San Diego astrophysicist Adam Burgasser, a co-author of the study. "This is due to their roughly spherical distribution around the Milky Way, as opposed to the more familiar flat disk of younger stars that include the Sun."

Wikipedia's Formation of galactic halos says

The formation of stellar halos occurs naturally in a cold dark matter model of the universe in which the evolution of systems such as halos occurs from the bottom-up, meaning the large scale structure of galaxies is formed starting with small objects. Halos, which are composed of both baryonic and dark matter, form by merging with each other. Evidence suggests that the formation of galactic halos may also be due to the effects of increased gravity and the presence of primordial black holes. The gas from halo mergers goes toward the formation of the central galactic components, while stars and dark matter remain in the galactic halo.
On the other hand, the halo of the Milky Way Galaxy is thought to derive from the Gaia Sausage.

"Halos... form by merging with each other" isn't profoundly instructive, but I'm guessing it means that there are small inhomogeneities and the coalesce into larger ones without a lot of rotation being involved (thus the spherical shapes). I suppose the part about the Gaia Sausage means that the Milky way is not a good example of a disk-shaped galaxy forming at a spherical halo.
Question(s):

But how do disk-shaped galaxies then form at the sites of the spherical halos?
Do stars in the halo just sit there without rotating, or perhaps slowly accelerate towards the gravitational center?


texts: Can the lensing effect of Sagittarius A* be used to image the stars diametrically opposite to the sun?

texts: The sun can magnify an image of a source 100 ly away nearly 100 billion times, if the ring is captured from the nearest focal point (550AU). According to Christian Ready of Launch Pad Astronomy, we can image objects closer than 100 ly even more precisely. If this is the case, then, given that we are much much far away from Sag A*'s nearest focal point, and that the ratio of our distance from lens to the object we want to observe is much much higher than the 550 AU to 100 ly ratio for the sun, can't we image the stars on the exactly opposite side of the milky way, along the focal line of Sag A*? If yes, how precise will we be, in imaging them as well as their planets (and moons, if possible)? On that side, what is the minimum distance of an object from Sag A*, that can be imaged on earth? Can the distinct stars in the globular cluster be imaged this way? Also, can we use the sun and Sag A* as a combined lens to obtain better images?


texts:
The sun travels in an arc across the sky. Where I live, during the summer the arc rises higher, but in the winter the arc is lower. Once might speak of highest altitude or elevation the sun reaches during any given day. In the old days this was called "high noon" when the sun had reached the highest point in the sky for that day. The town clock would be set to 12 at this point.

Is there a term for the elevation of the sun in the sky?


texts: Where do local users of ALMA live and work?

texts:
These days with high speed internet, observational astronomy can be done from remote locations. Still I believe from time to time an experimenter might travel to work on-site for particularly challenging or unusual/non-standard observations, where working closely with the instrument support team is necessary.

When astronomers travel to the Atacama Large Millimeter Array or ALMA:

Where do they live?
Where do they work during observing sessions?

Representative photos would be greatly appreciated!

I'm guessing it looks a little different than this:

Source: Cropped from Apertif - the focal-plane array system for the WSRT

  Figure 2. The WSRT telescope RT5 equipped with the APERTIF prototype. Shown in the inserts is the Vivaldi array in the lab (top right) and in the focal plane of the telescope (bottom right).


texts: What are the dark spots in the "face of Mars" picture?

texts: In this picture of Cydonia by Viking 1 (taken from this article), there are a bunch of black spots scattered everywhere. Are they an artifact of the image or are they an actual feature on the surface of Mars?


texts: Why do nebulae turn into accretion disks but planets do not?

texts:
What are the factors that prevent planets from also turning into disks, like the stellar dust in a nebula does?

The Earth is not a perfect sphere, but rather it's squished at the poles and it bulges at the Equator, owing to its rotation working to squish it into a disk.

I'm tempted to say that the Earth couldn't become a disk because of the density of the material in it fighting back against being pressured into a disk in a way that in stellar gas you can't? But then, why isn't the gas around the gas giants a disk? Is it because of the solid nucleus of those planets fighting against that?


texts: What would we find if we could travel 786 trillion light years in any direction

texts:
I've sometimes heard of galaxies that are millions or billions of light years away but if we could instantly travel 786 trillion light years in any direction, what are we likely to find? And what if we continued on for another 786 trillion light years?

PS: I'm not a physicist.


texts:
The universe supposedly started off with equal parts matter and antimatter and they are said to annihilate each other. Also, nature is famous for it's balance between everything. So all we see is matter and no antimatter (I guess that's a good thing, we would all have been annihilated otherwise), so where did all the antimatter go?

Also, does antimatter exist in the same space as matter? What are the leading theories about it?